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Biomedical subjects

G Becker

Publications and source records attributed to G Becker.

At least 19 recordsLinked to original sources
PubMed1997

Comparison of transcranial sonography, magnetic resonance imaging, and single photon emission computed tomography findings in idiopathic spasmodic torticollis.

Various lines of evidence suggest that the basal ganglia and thalamus are involved in the pathogenesis of idiopathic dystonia, but unfortunately neuroradiological and pathological data are sparse and controversial. In this study, we have examined 10 patients with spasmodic torticollis by neuroimaging techniques, including transcranial sonography (TS; n = 10), conventional (n = 10) and diffusion-weighted (n = 5) magnetic resonance imaging (MRI), and single photon emission computed tomography (SPECT; n = 10), employing [123I]iodobenzamide (IBZM) as a ligand with a high affinity to the D2 receptor. In seven patients, TS showed small hyperechogenic lesions in the medial segments of the lentiform nucleus contralateral to the side of head deviation. In accordance with the site of TS abnormalities, diffusion-weighted MRI displayed a hyperintense lesion in only one patient, while standard MRI of this area was normal in all patients. SPECT revealed a slight but statistically nonsignificant reduction of IBZM tracer uptake in an area corresponding to the dorsal portions of the striatum in 9 of the 10 patients. TS findings support the hypothesis that structural alternations of the pallidothalamic circuit contralateral to the side of head deviation are involved in the pathogenesis of idiopathic spasmodic torticollis. TS may be more sensitive in detecting basal ganglia alterations than MRI.

Adult↗
PubMed1997

Rescue therapy with tacrolimus in simultaneous pancreas/kidney transplantation.

Tacrolimus has been effective both in primary and rescue therapy following steroid and OKT3-resistant acute rejection in liver and kidney transplantation. Due to the effects of tacrolimus on glucose metabolism, there has been concern about its use in simultaneous pancreas/kidney transplantation. We report on the results of six patients (three female, three male, age 35.2 +/- 7.3 years) converted from cyclosporin A to tacrolimus following simultaneous pancreas/kidney transplantation in steroid-resistant acute rejection. Tacrolimus was induced 2.8 +/- 1.7 months (range 1-4.8 months) after transplantation; follow-up was 3-18 months. Following conversion, creatinine levels declined in all patients [3.5 +/- 1.2 mg/dl before conversion, 3.0 +/- 1.9 mg/dl (n = 6) at three months, 1.4 +/- 0.1 mg/ dl at 1 year (n = 3)]. Before conversion, fasting blood glucose levels averaged 154 +/- 33 mg/dl, with three patients receiving insulin. Three months later no patient required insulin, the mean glucose level being 107 +/- 23 mg/dl (n = 6); at 1 year it was 92 +/- 9 mg/dl (n = 3). One patient lost his pancreatic graft after 4 months due to a mycotic aneurysm. We conclude that conversion to tacrolimus is a safe and effective treatment in cases of steroid-resistant rejections following pancreas/ kidney transplantation.

Administration, Oral↗
PubMed1996

Primary T-cell lymphoma of the cerebellum. A case report.

Most primary CNS non-Hodgkin lymphomas are of B-cell lineage. Only a very few immunocytochemically well documented cases of T-cell lymphomas have been reported. We report a case of a high malignant T-cell lymphoma localized primarily to the vermis of the cerebellum and compare the characteristics of the clinicopathological presentation with those of B-cell lymphomas as well as with the other T-cell lymphomas reported.

Aged↗
PubMed1996

Correlation of intra-operative ultrasound with histopathologic findings after tumour resection in supratentorial gliomas. A method to improve gross total tumour resection.

The aim of this study was to evaluate whether intra-operative ultrasound (= IOUS) is a suitable tool to detect residual tumour tissue after gross total resection in supratentorial gliomas. During a period of 18 months 45 patients with supratentorial gliomas (38 high-grade and 9 low-grade, according to the WHO-grading system [42]) were operated on. A series of 78 biopsies was taken from the resection cavity under continuous sonographic control at the end of surgery. Gross total tumour resection was intended in 34 patients (= 76%). The biopsy specimens were matched with the sonographic features at each biopsy site. The sonographic appearance of the resection margins were classified into 2 groups: (1) Irregular hyperechoic areas extending from the cavity into the iso-echogenic brain tissue and (2) a dense small (< or = 3 mm in diameter) rather regular hyperechoic rim surrounding the resection cavity. 47 out of 53 biopsies taken from hyperechoic areas (group I) (36 high-grade/11 low-grade) revealed solid tumour tissue (= 89%). 34 (= 72%) of these 47 areas were microscopically assessed as inconspicuous by the surgeon. 6 samples (4 high-grade/2 low-grade) contained tumour infiltration zone. 25 biopsies (23 high-grade/2 low-grade) taken from the hyperechoic rim [group 2] were diagnosed as follows: Normal brain tissue in 11, tumour infiltration zone in 8 and solid tumour tissue in 6 cases. Of 34 cases with "gross total removal" according to the surgeon's assessment 25 showed sonographic signs of residual tumour tissue, which was confirmed histologically as solid tumour tissue in 22 of these cases. It is concluded, that IOUS following resection of supratentorial gliomas can detect residual tumour tissue with high specificity and thus improve gross total resection. However, a thin hyperechoic rim surrounding the resection cavity (less than 3 mm in diameter) is a non-specific finding, which can mask thin residual tumour layers and therefore needs further evaluation of its nature.

Biopsy↗
PubMed1996

[Gamma knife versus stereotactic linear accelerator. Utilization, clinical results and cost-benefit relations].

INTRODUCTION: The principles of radiosurgery were developed in 1951 by Leksell. Their technical realization led to the development of the gamma knife and stereotactically modified linear accelerator. METHODS: In addition to the gamma knife, we present the different principles of convergent beam irradiation (radiosurgery with linear accelerator), the further development to fractionated stereotactic conformal radiotherapy, and the necessary quality-assurance steps. RESULTS: The greatest uncertainties in the precision of radiosurgery result from medical imaging (CT 0.7 x 0.7 x 1 mm; DSA 1-5 mm; MR angiography < 2 mm). The focusing accuracy of the gamma knife (+/- 0.3 mm) can also be achieved today by linear accelerators using a stereotactic floorstand. For the same indication and the same dosage for the target volume, there are no clinical differences between the gamma knife and the linear accelerator (AVM: 80% complete obliteration; metastases: 85% local tumor control; AN: 90% tumor control). However, there are greater differences in costs. There is no constellation where the gamma knife is just as expensive or more cost-effective than the linear accelerator treatment. The most cost-effective solution is modification of an available linear accelerator, resulting in treatment costs per patient of 9,201.25 DM (50 patients/year). CONCLUSION: There seem to be no methodological, physical, clinical or cost reasons for using a gamma knife, especially because the trend is going towards fractionated conformation radiotherapy instead of the application of high single doses.

Brain Neoplasms↗
PubMed1996

Treatment planning for bicentric stereotactic irradiation.

We have investigated a bicentric stereotactic convergent beam irradiation technique for the treatment of irregularly shaped, especially elongated, target volumes. Depending on the size and shape of the target volume optimum values for the isocenter distance, collimator apertures and dose inhomogeneity have been determined which serve as starting parameters for the interactive optimization of dose distribution. The treatment planning system of the stereotactic unit SRS-200 (Philips) has been used to calculate the parameter tables. However, the presented results are also applicable to other stereotactic systems.

Film Dosimetry↗
PubMed1996

Diltiazem minimizes tubular damage due to FK506-mediated nephrotoxicity following ischemia and reperfusion in rats.

We examined the nephrotoxicity of tacrolimus (FK506) in a model of mild warm ischemia. After clamping of both renal arteries of male Sprague-Dawley rats for 20 min, the animals received tacrolimus (3 mg/kg/day i.p.), vehicle of a combination of tacrolimus (3 mg/kg/day i.p.) and diltiazem (12 mg/kg, orally) or vehicle and diltiazem (12 mg/kg, orally). The excretion of urinary enzymes was determined on a daily basis, creatinine clearance at day 10. Tacrolimus significantly increased NAG (N-acetyl-beta-glucosaminidase) excretion and associated histological damage, finally decreasing creatinine clearance. The toxic potential of tacrolimus was markedly enhanced by ischemia. The additional application of diltiazem reduced NAG excretion and histological damage without affecting creatinine clearance. Thus, the protective effect of diltiazem on tacrolimus-induced nephrotoxicity seems to be at least partially a tubular one.

Acetylglucosaminidase↗
PubMed1996

Clusterin (Apo J) protects against in vitro amyloid-beta (1-40) neurotoxicity.

Clusterin is a secreted glycoprotein that is markedly induced in many disease states and after tissue injury. In the CNS, clusterin expression is elevated in neuropathological conditions such as Alzheimer's disease (AD), where it is found associated with amyloid-beta (A beta) plaques. Clusterin also coprecipitates with A beta from CSF, suggesting a physiological interaction with A beta. Given this interaction with A beta, the goal of this study was to determine whether clusterin could modulate A beta neurotoxicity. A mammalian recombinant source of human clusterin was obtained by stable transfection of hamster kidney fibroblasts with pADHC-9, a full-length human cDNA clone for clusterin. Recombinant clusterin obtained from this cell line, as well as a commercial source of native clusterin purified from serum, afforded dose-dependent neuroprotection against A beta (1-40) when tested in primary rat mixed hippocampal cultures. Clusterin afforded substoichiometric neuroprotection against several lots of A beta (1-40) but not against H2O2 or kainic acid excitotoxicity. These results suggest that the elevated expression of clusterin found in AD brain may have effects on subsequent amyloid-beta plaque pathology.

Amyloid beta-Peptides↗
PubMed1996

Cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease: assessment with dynamic susceptibility contrast-enhanced MR imaging and the acetazolamide stimulation test.

PURPOSE: To quantitatively assess cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease. MATERIALS AND METHODS: In 21 symptomatic patients with occlusive cerebrovascular disease, magnetic resonance (MR) imaging was performed with a 1.5-T system. Before, during, and after a brief bolus injection of gadopentetate dimeglumine into the antecubital vain, a series of 32 rapid T2*-weighted gradient-echo images of two different sections were acquired simultaneously to measure the concentration-time-curves in the brain tissue and in the brain-feeding arteries. Principles of indicator dilution analysis were applied to compute regional cerebral blood flow (rCBF) and volume. Each patient underwent two examinations, the first before and the second after acetazolamide stimulation. RESULTS: In the asymptomatic hemisphere, a mean increase in rCBF value of 47.1% was observed after acetazolamide stimulation. In the affected areas of the symptomatic hemisphere, a statistically significantly reduced response to acetazolamide stimulation was found, indicating a severely compromised cerebrovascular reserve capacity. CONCLUSION: MR imaging with the described techniques provides quantitative information about the cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.

Acetazolamide↗
PubMed1996

Lenticular nucleus lesion in idiopathic dystonia detected by transcranial sonography.

We report the transcranial sonography (TCS) findings of the basal ganglia in 86 patients with dystonic disorders including idiopathic dystonia (facial, cervical, upper limb, and generalized dystonia), drug-induced tardive dystonia, dopa-responsive dystonia, and kinesigenic dystonia. The TCS was focused on alterations of the lenticular, caudate, raphe nuclei, and the thalamus. Seventy-five percent of patient with idiopathic cervical and 83% of those with idiopathic upper limb dystonia had a hyperechogenic lesion of the middle segment of the lenticular nucleus on the side opposite to the clinical dystonic symptoms. The ipsilateral side was also affected in 20%. In facial dystonia, only one-third of the patients revealed lenticular nucleus lesions. The mean area of the lenticular nucleus lesion opposite to the clinically affected side was 30 mm2 in cervical dystonia, 17 mm2 in upper limb dystonia, and 7.5 mm2 in facial dystonia. These lenticular abnormalities were significantly more frequent (p < 0.001) and their areas were significantly greater (p < 0.001) compared with a control group of 50 patients afflicted with radiculopathy. There was a significant correlation of the severity of symptoms with the intensity of lenticular nucleus hyperechogenicity in patients with cervical and upper limb dystonia (p < 0.05). Increased caudate nucleus echogenicity was present in 20% of patients with cervical and upper limb dystonia, mostly contralateral to the clinically affected side and raphe abnormalities were present in 7% of all patients with idiopathic dystonia. In contrast, there were no abnormalities of the lenticular nucleus or thalamus in nonidiopathic dystonias. We conclude that idiopathic dystonia is associated with lesions in the basal ganglia, particularly the lenticular nucleus, that can be visualized by TCS. An alteration of the basal ganglia matrix may be the pathologic basis of idiopathic dystonia with secondary affliction of striatopallidothalamic pathways.

Adult↗
PubMed1996

[Stereotaxic convergent-beam irradiation. Initial experiences with the SRS 200 system].

BACKGROUND: The system SRS 200 for the stereotactic convergent beam irradiation described in this paper has a stereotactic floor stand, which allows the high precision rotation of a secondary collimator around an isocenter. This system is used since 1991 at the University Hospital of Tübingen for the treatment of patients with solitary brain metastases, acoustic neurinomas and arteriovenous malformations. PATIENTS AND METHODS: The attainable accuracy of the mechanics and dosimetry was studied within the scope of extensive quality assurance measures during its installation and before each patients' irradiation. The individual treatment steps from radiotherapy planning to irradiation were evaluated by means of a specially developed head phantom. Since the installation of the SRS 200 a total of 50 patients (21 solitary brain metastases, 12 acoustic neurinomas, 17 arteriovenous malformations) has been treated with the system. RESULTS: With 0.3 mm +/- 0.2 mm an excellent accuracy of the target point transfer and isocenter stability during irradiation was attained. The difference between calculated dose and dosimetric control measurements was smaller than 3%. The physical accuracy, however, is limited by the imaging resolution (CT and digital subtraction angiography). Of the patients 15% with solitary brain metastases developed complete remission, 20% partial remission and with 50% no further neurological deterioration was observed. Imaging revealed for 88% of the patients a reduced uptake of contrast medium or a regression of the tumor size. Six patients with acoustic neurinoma had anacusis already before radiotherapy. Regarding the other patients in the follow-up, hearing improved in 1 patient, 1 patient showed hearing deterioration, and all other patients hearing remained constant. MR and CT imaging revealed in 10 patients with acoustic neurinoma a reduced uptake of contrast medium and in 1 patient a tumor diminution. From the patients with arteriovenous malformation only 4 have been followed for more than 2 years after treatment. Therefore, statements about the rate of obliteration are not possible yet. Concerning pretherapeutic symptoms (headache 22%, convulsion 28%, neurological deficits 11%) 8/17 (47%) of the arteriovenous malformation patients showed an improvement, in 8 patients clinical findings were unchanged and 1 patient showed neurological deterioration. CONCLUSION: The stereotactic system SRS 200 allows an excellent mechanical accuracy in the radiosurgery with linear accelerators.

Adolescent↗
PubMed1996

Transcranial duplex-sonography in intracranial hemorrhage. Evaluation of transcranial duplex-sonography in the diagnosis of spontaneous and traumatic intracranial hemorrhage.

The aim of this prospective clinical study was to evaluate the potential of bedside transcranial color-coded duplex sonography (TDS) in the assessment of patients with acute intracranial hemorrhage and respective complications. 74 patients (35 with spontaneous and 27 with traumatic hemorrhage, 12 excluded due to insufficient insonability) underwent 152 TDS examinations. The results were compared to computer-tomography (CT) as well as conventional transcranial Doppler sonography (TcD). The size and localisation of intracerebral hemorrhages as detected in TDS coincided in 39/42 examinations with CT findings; in cases of traumatic intracranial extracerebral hematoma TDS correlated in all but one case (18/19). The TDS findings for the diameter of third and lateral ventricles (n = 126) as for midline-shift (n = 26) showed a good correlation (p < 0.0005) to CT-measurements. TDS appears to be a useful bedside, non-invasive tool in order to detect and exclude intracranial complications in patients with intracranial hemorrhages.

Cerebral Hemorrhage↗
PubMed1995

Reduced echogenicity of brainstem raphe specific to unipolar depression: a transcranial color-coded real-time sonography study.

Echogenicity of the brainstem raphe was assessed in patients with major depression, bipolar affective disorders, and schizophrenia and compared with healthy adults employing transcranial color-coded real-time sonography. Forty probands were enrolled in each group. A highly significant reduction in raphe echogenicity was detected only in patients suffering from major depression. Echogenicity of the raphe was independent of age or sex and did not correlate with severity of the depressive syndrome or patient state. These findings are suggestive of structural desintegration of the brainstem raphe in unipolar depression, an anatomical region assumed to be a biological focus in the pathogenesis of depressive syndromes.

Adult↗
PubMed1995

Stereotactic convergent beam radiosurgery versus stereotactic conformation beam radiotherapy.

By means of preliminary results in the treatment of patients with acoustic neurinoma the achievable accuracies, dose distributions and time consumption of stereotactic LINAC-based convergent beam radiosurgery are compared to those achieved with fractionated stereotactic conformation beam radiotherapy. Characteristics of both techniques are described. With the Tübingen radiosurgery system a good adaptation of the dose distribution to spherical or oval target volumes with a steep dose gradient was achieved, whereas homogeneity and adaptation of the dose distribution to irregularly shaped targets were better with the Heidelberg conformation technique. The mechanical accuracy of the Tübingen floorstand system was 0.3 mm +/- 0.2 mm, and that of the Heidelberg mask fixation system < 1 mm. Both methods require similar total treatment times. Nine patients were treated by the Tübingen radiosurgery system. The results are compared with 12 patients treated by conformation radiotherapy in Heidelberg. In both patient groups no further tumour growth occurred. Four of 9 single dose treated patients developed side-effects, such as temporary trigeminal and facial paraesthesia hearing deterioration and oedema. In contrast, patients treated by fractionated radiotherapy showed no side-effects. Relating to the short follow-up the results indicate that single dose application has certain drawbacks for special indications. Further studies have to work out which method gives the best treatment results.

Adolescent↗
PubMed1995

Unidirectional fluxes of short-chain fatty acids across segments of the large intestine in pig, sheep and pony compared with guinea pig.

Unidirectional fluxes of short-chain fatty acids across pig, sheep and pony caecum, proximal and distal colon were studied under short-circuit current conditions in Ussing chambers. Findings are compared with results from guinea pig. Marked species differences are apparent; highest mucosal-to-serosal fluxes of acetate, propionate and butyrate were seen in guinea pig, lower values in pig and smallest fluxes in sheep and pony. Segmental differences between caecum, proximal and distal colon exist mainly in guinea pig and are less developed in pig, sheep and pony. Inhibition of Na+/H+ exchange by amiloride added to the mucosal solution decreased the mucosal-to-serosal fluxes of short-chain fatty acids clearly in guinea pig caecum and proximal colon, and very little in distal colon. This effect was somewhat less pronounced in pig caecum and distal colon, in caecum and distal colon of sheep and caecum of the pony. In pig, sheep and pony proximal colon and pony distal colon no significant inhibition was observed. Inhibition of the K(+)-H+ ATPase by addition of ouabain to the mucosal solution diminished mucosal-to-serosal fluxes of short-chain fatty acids in the guinea pig distal colon extensively. No comparable inhibition was seen in any of the other segments in the animals studied.

Amiloride↗
PubMed1995

Abdominal wall metastasis following percutaneous endoscopic gastrostomy.

Percutaneous endoscopic gastrostomy (PEG) has become a widely used method for nutritional support, particularly in patients with advanced head and neck carcinomas. Since the method is easy and widely established it is necessary to assess possible complications, even rare ones. In this paper we report on two patients with vaccination metastasis following PEG insertion. Both patients had advanced squamous cell carcinoma of the head and neck or the upper esophagus. In three patients previous bougienage was performed, because of considerable stenosis of the pharynx and/or esophagus. Fast-growing metastases were found at the site of PEG insertion, with and without involvement of the gastric wall. In neither case was abdominal wall metastasis the cause of death. There is a small but definite risk of tumor seeding into the abdominal wall after PEG insertion for obstructive malignant tumors. The clinical impact of this finding, however, is still undefined and needs further investigation.

Abdominal Muscles↗